Very little to do with actual standard, rather the hardware that can make use of it. As was mentioned earlier, 100G ethernet, Optane, 4x Titan X(x) & so many other devices will probably need something like 16x PCIe 5.0 in the future.
Gaming gains are minimal but there are already many other devices that have the potential to saturate the current PCIe 3.0 bus on regular desktops.

Very little to do with actual standard, rather the hardware that can make use of it. As was mentioned earlier, 100G ethernet, Optane, 4x Titan X(x) & so many other devices will probably need something like 16x PCIe 5.0 in the future.
Gaming gains are minimal but there are already many other devices that have the potential to saturate the current PCIe 3.0 bus on regular desktops.

New Member

It depends a lot on the game. The last figures I saw from benchmark articles were from years back, so they are not valid any longer with today's GPU power. On my old PCI-E 2.0 rig I noticed a big bottleneck in many games when I had plugged my GTX 1050 Ti to an x8 slot mistakenly. Also there are certain games that are bottlenecked by 2.0 x16 as well, one of them is rFactor 2 (discussed here).